Is that their goal, or is that the deal they get. Every fight on mainstream cable is heavyweight, I guess because heavywights is more appealing to none boxing fans, however the lighter weight divisons are way more entertaining.

Is it cause they have a deal for heavyweights? Or is it cause all the fighters at lower weight classes just dont want to fight on anything that isn't HBO or showtime?

They're just going with what Kathy Duva has since the deal is with Main EVents. Gabriel Rosado isn't a heavyweight and he's been probably pushed the the most on NBC sports. They also had Zab Judah on not too long ago.

It's probably because HBO has abandoned the heavyweight division. NBC can see itself having a monopoly on the heavyweight division in America.

You're wrong about the heavyweight division appealing to "none" fans. I like heavyweights because they would beat the fighters in the divisions below. It's similar to how the heaviest division in weightlifting is appealing because these men lift the most weight.